Honing or polishing tool



L April 1943- A. KRASTIN 2,316,257

HONING OR POLISHING TOOLS Filed Feb. 5, 1941 INVENTOR. x4/F/VOZD AIWSr/A ATTORNEY.

Patented Apr. 13, 1943 UNITED STATES PATENTOFFICE Arnold Krastin,Cleveland, Ohio Application February 3, 1941, Serial No. 377,173

6 Claims.

This invention relates to a tool for performing surface finishingoperations on hollow members, for example for honing hydraulic brakecylinders and the like.

An object is to provide a surface finishing tool which is self-fittingwith respect to circular surfaces of different diameters.

Another object is to provide a surface finishing tool capable ofapplying, in a flexible manner and progressively around an internalcircular surface, finishing operations of equal effective force atequally spaced regions.

A specific object is to provide a simple and inexpensive finishing toolfor internal cylindrical surfaces, which tool can be mounted in thechuck of a portable machine on the order. of an electric drill anddriven thereby properly to perform honing or polishing operations onbores of different sizes without requiring precise alignment between thetool chuck and the work.

A still more specific object is to provide a tool for reconditioninghydraulic brake cylinders e. g. of automobiles when such cylindersbecome pitted or scored, which tool will operate properly both on thewheel cylinders and the master cylinders notwithstanding a considerabledifference in diameters therebetween.

Other objects and the various novel features of the invention willbecome apparent from the following description of the illustrativeembodiments shown in the drawing in which:

Fig. 1 is a side elevation of a brake cylinder honing or polishing toolincorporating the invention, portions of the assembly being shown incentral longitudinal section;

Fig. 2 is anend view of the tool showing the relative position of partsprior to application to the work;

Fig. 3 is asectional detail view of a preferred connection between thetool head and driving shaft or shank;

Fig. 4 is a major face view of a flexible abrasive strip adaptedto bemounted on the tool head;

Fig. 5 is a view similar to Fig. 2 showing the relationship of partswhen the tool is applied, to the work, and v Fig. 6 is an end view of amodified form of tool, showing flexible tool blades thereof in normalposition and showing, in broken lines, working positions of such blades.

Brake cylinders become pitted mainly by corrosion, and sometimes scoreddue to accumulation on the plunger or piston of abrasive foreign matter.Reboring of the cylinders in order to recondition them when pitted orscored requires (Cl. E l-184.2)

and its use does not, in many cases, require dismounting of thecylinders.

Referring to Fig. l the head I of the tool comprises, as shown, twostrips of metal 2 and 3, secured together as by screws 4 and 5 which mayenter the strips from opposite directions as illustrated so as to clampbetween them flexible tool elements l5, l6 and I! to be later more fullydescribed. Each of the strips is threaded to receive one of the screwsso that the strips may be drawn into clamping relation to the flexibleelements. A driving shaft or shank 6 may comprise simply a section ofround metal stock with one end secured between outstruck portions I ofthe head strips 2 and 3, as by a cross pin 8. The outstruck portions 1of the head strips, as shown in Fig. 3. are oppositelycurved in crosssection and more or less loosely receive the end" of the shaft betweenthem when the strips 2 and 3 are in clamping position with respect tothe flexible elements, and the pin is slightly loose in the receivingopening, 9 of the shaft,so that the head, in effect, has a universaljoint coupling with the shaft. The universal. coupling enables the headcontinuously to operate on a working axis somewhat at an angle to theaxis of the driving chuck in which'the shaft is gripped and rotated.Thus if the driving machine is portable an operator can hold the chucksufficiently accurately in position by hand for proper operation; or ifthe machine is fixedly mounted the operator can hold the work by hand.The flexible elements l5, l5 and I! also cooperate in enabling properwork to be done notwithstanding slight angular displacement of work anddriving chuck axes.

The flexible element l5 is'preferably a rectangular strip or leaf oflight gage spring metal (e. g. phosphor bronze) so that unsupported endportions thereof can be easily flexed. The central part or portion l8 ofthe strip is preferably flat and extends a considerable distance beyondthe head strips 2 and 3 at opposite sides thereof as gripped by the headstrip, but the overall lateral extent of the portion I8 is less than thesmallest diameter of cylinders to be surfaced. The central flat part ofthe spring element l5 has openings to receive the screws 4 and 5 of suchsize that said central part cannot be clamped in a position eccentric tothe head. The free portions 20 of the spring element 15 beyond theattaching or mounting flat portion l8 as shown in Fig. 2'

are bent in opposite directions from the plane of the mounting portion,in expanding curved form i. e. spiral or other suitable curve, so thatsubstantial end marginal portions of the spring element lie outwardlyfrom the axis of the head greater distances than radii of the cylindersto be surfaced. The general S-shape of the spring element IS inunstressed condition is preferred because, this makes it easy to insertthe tool into the cylinder to be surfaced. The spring element l'i couldbe made in two pieces with portions overlapped at the center of the headfor attachment thereto.

The outwardly disposed faces of the expandingly curved portions 20 ofthe spring element l support or bear suitable abrasive for contact withthe walls of the cylinder to be surfaced.

Preferably the abrasive is supported separately from the spring elementIS. the elements IE and II above referred to being in the form offlexible rectangular sheets or strips having abrasive grains on one side(0. g. emery clothl. Such strips. (one shown in Fig. 4) have slots 2!leading inwardly from one edge so that the slotted margins can bereadily inserted between the spring strip portion I8 and the respectivehead strips 2 and 3 with the shanks of the clamping screws 4 and 5occupying the slots. The screws need merely to be loosened in order toremove and replace the abrasive strips l6 and I! as will be apparent.

With the arrangement of parts above described the flexible curvedportions of the S-shaped spring element I5 and strips l6 and II can befitted into substantially complementary relationship to cylinders ofdifferent diameters and the free portions of the spring arms applyapproximately equal polishing or honing pressure and driving torque atopposite portions of the work surface to be honed or polished. Fig. 5shows the working relationship of the curved spring portions andabrasive strips to a cylinder C to be honed or polished. All portions dfthe abrasive strips which contact with the cylinder C and all portionsof the spring l5 which support said portions of the abrasive are intrailing relation to the connections thereof to the head I; and theconnections. by which driving torque is effected are flexible so thatdriving torque and abrasive pressure are flexibly applied. Due to theflexibility of the tool elements l5. l6 and I! and the manner ofsupporting them it is apparent that, when the head I is rotatedclockwise'as shown in Fig. 5, practically the entire areas of each ofthe curved portions of the strips l6 and II can become effective inabrading the inner surface of the cylinder,centrifugai force aiding thetendency of the free spring end portions to assume a form complementaryto the cylinder and in accomplishing uniform working pressure atcircumfercntially spaced regions corresponding to the number of freespring portions used. This number may. of course. be increased. Theabrasive pressure may be greater at portions of the spring element l5near the attached portions [8 thereof or near the end portions or atintermediate regions, but always the Zones of concentrated pressure arebalanced circumferentially about the working axis of the tool head; and,due to the uniform flexibility of the spring element at all freeportions thereof lengthwise of the head the zones or regions ofconcentrated pressure will extend longitudinally of the work fortheentire length of the portion operated upon by the tool at a given time.

In order to assist in initially aligning the tool with the cylinder orother surface to be honed or polished I may provide tool-aligningmembers such as shown at 25. These, as shown, are pins which arethreaded (e. g.) into necked portions 26 of the head strips 2 and 3, sothat the pins can. in operative effect. be lengthened or shortened inaccordance with the inner diameters of different elements constitutingthe work. The tool aligning members exert no pressure on the flexibleelements, but simply serve, at the start of the honing or polishingoperation, to secure approximate alignment of the tool driving chuckwith the surface of the member to be honed or polished.

In order to simplify the matter of loosening and tightening the clampingscrews 4 and 5, holes are provided in the spring element l5, as at 23for reception of a screw driver,-the holes lying substantially oppositethe heads of respective screws.

Fig. 6. illustrates three flexible members l5a which extend normallyoutwardly parallel to supporting surfaces of a triangular head la.Abrasive strips could be supported thereby in approximately the samemanner as already described. In such case the triangular piece la wouldordinarily be bar'stock with a socket at one end to receive the drivingshaft 6 and connecting pin 8, and the clamping strips 38 would befastened to the triangular body as by three sets of screws 3|. Alignmentsecuring members 32, corresponding in operative effect to the members25, are plates adjustable in and out on the outer faces of the clampingstrips 30 (e. g. having slots to receive the shanks of the screws 3| topermit movement in and out on part of the alignment securing plates).

The arrangement according to Fig. 6 is characterized principally in thatthe spring leaves l5a are capable of operating to force abrasive against(e. g.) cylinders of greater variation in diameter than is possible bythe arrangement according to Fig. 2 in the exact form illustrated, i. e.wherein the minimum diameter of the work is the length of the centralportion l8 of the spring element IS. The arrangement according to Fig. 2could be modified in accordance with Fig. 6, in other words could havewholly straight oppositely extending readily flexible spring armelements.

I claim:

1. A honing or polishing tool for internal circular surfaces, comprisinga rotatable head and a plurality of flexible abrasive members extendingoutwardly therefrom with free portions adapted to extend in trailingrelationship to the head in the working position of the members so thatportions of the members are complementary to the circular surface,relatively separable substantially rigid clamping strips on the head.and releasable means supported by said clamping strips and operable toforce the strips toward each other in a manner to cause the clampingstrips to grip and hold portions of the flexible members between them.

2. A honing or polishing tool comprising a drive shaft adapted forrotation, a generally shaped one piece metallic leaf spring element,means lying on opposite sides of said element connected with the driveshaft and extending along the axis thereof beyond one end of the shaftfor supporting said element intermediately of its ends, and abrasivemeans supported by outwardly disposed portions of the arms of the S-shaped element for contact with the work. 7

' 3. In a honing or polishing tool, a head comprising a pair ofsuperposed strips of relatively rigid material and means connecting thestrips and operable to force the strips together, a shaft, meansconstituting a universal coupling between the strips and shaft, andflexible means clamped between the strips and adapted for pressingabrasive material outwardly against a circular surface when the shaft isrotated.

4. A honing or polishing tool comprising a rotatable head, flexibleelements attached to the head and emanating therefrom and arranged tooperate in contact with a circular surface in trailing relation to theattached portions of said elements, and means projecting laterally fromthe head in a manner approximately .to center the head with reference tothe work.

5. The arrangement according to claim 4 wherein said means compriseoutwardly and inwardly adjustable members projecting from the head atdifferent points along the working axis of the head.

6. In a honing or polishing tool, a rotatable head comprising separableclamping members, a leaf element clamped between the members and adaptedto extend outwardly from the head and then in generally trailingrelation to the clamped portion in respect to the direction of rotationof the head, clamping screws connecting the clamping members, and aflexible abrasive strip marginally clamped between said members, themargin so clamped being slotted inwardly from the edge of the flexiblestrip so that, without removing the screws, the strip can be mounted inclamping position with the screws extending through the strip.

ARNOLD KRASTIN.

